Printing ink base



' Patented Aug. 4, 1931- UNITED STATES PATENT OFFICE GEORGE D. KNIGHT, OF REDWOOD CITY, CALIFORNIA, ASSIGNOR TO EMORY WINSHIP,

. OF SAN FRANCISCO, CALIFORNIA PRINTING INK BASE No Drawing. Application filed April 16, 1924-, Serial No. 706,881. Renewed June 30, 1927.

- The invention relates to a printing ink and particularly to the base, vehicle or carrier towhich the pigment is added to produce the finished ink.

An object of the invention is to produce an intaglio or engraving ink.

Another object of the invention is to produce a non-inflammable intaglio ink.

Another object of the invention is to prom duce an intaglioink which will redissolve in thefetchin of the printing cylinder when .the rotogravure press is started after a temporary shut down.

Another object of the invention is to provide an ink in which no stratification occurs and in which there is no sedimentation of the pigment.

Another object of the invention is to provide an intaglio ink which resists removal by water after printing. A further object of the invention is to provide a satisfactory and inexpensive intaglio ink and a process of making the same.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description, where I shall outline in full the preferred form of the ink of my invention and the method of making the same.

The ink base of my invention consists principally of a colloidal solution of gelatin and casein. The gelatin is preferably animal glue and the casein may be derived from any suitable source. While I have made successful rotogravure ink from a colloidal. solution of glue, casein and water, plus a suitable casein solvent such as ammonia, I find that better results are obtained by employing skim milk as the source of casein. Besides containing sufficient casein, the skim milk contains other ingredients, such as sugar of milk, albumen, and mineral salts, which apparently have a beneficial effect upon the resulting product. Further, the casein contained in milk is cheaper than separated casein so that by employing skim milk, I not only produce a better product, but a cheaper product. Skim milk contains approximately ninety percent water, three percent casein, and five percent milk sugar, seven tenths percent albumin and two tenths percent fat. While I prefer to use skim milk as the source of the casein, it is to be understood that I do not limit myself to the use of skim milk, for this purpose, since separated casein may be used.

If the ink, or the ink base is to be stored for any considerable length of time before being used, I add a preservative to the solution to prevent the decomposition of the glue and such preservative is preferably an oxidizing agent, such as an alkali bichromate. I have employed potassium bichromate successfully. solution is offensive, the odor may be masked by adding a strong smelling oil, preferably a pungent oil, such as citronella oil, and this oil'acts also as a preservative.

' I find that by adding a vegetable oil to the;

mixture, the viscosity of the emulsion is increased and the ink pulls more readily from the intaglio cylinder or plate in the printing operation. By adding the vegetable oil, the

ink base is given a greater affinity for paper than for the metallic printing cylinder or plate. I have found that linseed oil satisfied these requirements satisfactorily. In the event that the ink base is too stiff, a small percentage of a hydrocarbon thinner may be,

added which dilutes, without destroying the emulsion.

When separated casein is employed it is mixed with a suitable solvent, such as an aqueous solution of ammonia to produce solution of substantially the same proportions as occur in skim milk. When skim milk is employed the ingredients are mixed together in approximately the following pro- I have obtained very satisfactory results from a mixture of 75% skim milk and from 14% to 16% of glue and the other ingredicontainer. jected to a temperature of from 140 C. to

ents as given above. When vegetable oil is not used the percentage of the citronella oil should be increased, to approxiately 4%. Any suitable oxidizing agent may be employed and while I have used potassium bichromate, other metallic ,bichroma'tes such as sodium and ammonium maybe used with substantially equal effects. WVhen separated casein is used the percentage of the bichromate is increased. I

In making the ink base from skim milk the glue is first soaked in cold skim milk and the mixture is then heated to a temperature below the boiling point. The mixture is then introducedinto a closed container, or

the container within which: it is mixed is closedand the mixture is subjected to heat to sixty pounds to the square inch within the The mixture is therefore sub- 150 .C. and the pressure: and temperature are maintained for from one to three hours toinsure the proper results. I have found that if the mixtureis not boiled under pressurethat ltWlli gelatmize on cooling.

ifter the mixture has been heated in the closed container for the proper amount of time it is permitted to cool in the closed vessel, while under pressure, and, by following this methed the cooled material remains in liquid form. After being cooled, the liquid is filtered to remove lumps.

I have found that it is desirable to add the bichromate and the linseed oil to the mixture while it is hot, that is at approximately 80 (1., and also to add the pigment while the mixture is at this temperature to obtain thorough dissemination ofthe pigment and to prevent settlement thereof, which has a tendency to occur if the pigment is added to the mixture after it has cooled. I have made successful ink by'mixing from 90 to 110 parts by weightof pigment with 100 parts by weight of the base or'vehicle so that the finished ink-contains from 45% to- 55% of pigment. The pigment used was a mixture ofmanganese oxides, but oxides of other metals may be added, depending upon the color desired.

The bichromate or other oxidizing agent added to the mixture helps to fix it and also assists in preventing the removal of the ink from the paper after printing. The citronella oil is preferably added to the mixture after it has coo-led to substantially normal room temperature. By following this procpress is shut down, with a borax solution. Due to 'thenon-inflammable nature of the ink, the press may be run at high speed since there is no. danger of ignition.

I claim:

r 1.. An intaglio ink including casein dissolved in an aqueoussolution of ammonia combined with another glue.

2. An intaglio ink including casein dissolved in an aqueous solution of ammonia combined with animal glue.

3. An intaglio ink including casein dissolved in an aqueous solution of ammonia, and animal glue and an oxidizingagent,

4. An intaglio ink including casein dissolved in an aqueous solution containing ammonia, animal glue and an alkali bichromate.

[in intaglio ink including casein dissolved in an aqueous solution containing ammonia, animal glue, an oxidizing agent,. and a vegetable oil. 7 p r v 6. An intaglio ink including casein dissolved in an 1 aqueous solution containing ammonia, another glue, an oxidizing agent, a

deodorant and j a vegetable oil.

7. An intaglio ink including casein dissolved in an aqueous solution containing ammonia, another glue, and an alkali bichromate.

In testimony whereof, I have hereunto set f my hand.

' GEORGE n. KNIGHT.

ess I am enabled to produce a very effective from the metallic plate or cylinder, when the etching. V The ink may be readily washed 

